[Issue 20822] when building dmd, control characters for the console are included even when the host DC is piped

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20822

--- Comment #2 from Basile-z <b2.temp at gmx.com> ---
I've found a dubtful assulmption in build.d

https://github.com/dlang/dmd/blob/25e9247535649606e312f9e623be7a68b8d46678/src/build.d#L151-L157

"Since we're ultimately outputting to a TTY,"

                      ??????

"auto" should be the default. "auto" detects if the stuff is piped or not.

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